Characterization, evolution and IOCG

Characterization, evolution and IOCG-potential of the of
the Iron Range iron oxide mineralization, Belt-Purcell
basin, BC
Galicki, M. and Marshall, D. (SFU)
Anderson, B. and Enkin, R. (GSC)
Downie, C. and Gallagher, C. (EPL)
Outline
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Overview of the Iron Range
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Petrography
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Petrogenesis
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Geochronology (Paleomag)
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Base metal ore deposit potential
Overview of the Iron Range
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iron-oxide mineralization
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occurs along Proterozoic Iron Range Fault
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hosted within Proterozoic Aldridge Formation
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mainly deep-water sediments and turbiditic sequences
interbedded with gabbroic sills (Moyie sills)
Overview of the Iron Range
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iron-oxide mineralization
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occurs along Proterozoic Iron Range Fault
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normal, steeply west dipping fault
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reactivated multiple times
hosted within Proterozoic Aldridge Formation
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ore minerals: hematite, magnetite ± chalcopyrite
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mainly deep-water sediments and turbiditic sequences
interbedded with gabbroic sills (Moyie sills)
occur in massive lenses and vein
size
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length: ~ 3 km, width varies (20-50m), depth up to 200m
exploration history
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mineralization:
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various industry-driven efforts (e.g. CP Rail, Cominco)
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Eagle Plains Resources acquired Iron Range claims in 2000
(SEDEX/IOCG investigations)
Petrography
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two distinct mineralization types along the Iron Range fault:
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inner corridor of massive iron-oxides (mFeOx)
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flanked by brecciated iron-oxides (bFeOx)
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host to cpy-mineralization at depth
Petrography (mFeOx)
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massive iron-oxide mineralization varies in width between 20-40m
best exposed in 7 trenches between the Golden Cap and Rhodesia
showing
ore minerals are predominantly hematite with lesser magnetite and trace
pyrite and ilmenite
locally only hematite or predominantly magnetite with lesser hematite
euhedral to subhedral grains, large range of grain-sizes
multiple generations of hematite and magnetite precipitation (hematite
replacing magnetite and vice versa)
silica and carbonate alteration
Marshall and Downie, 2002
Petrography (mFeOx)
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Py
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hem
massive iron-oxide mineralization varies in width between 20-40m
best exposed in 7 trenches between the Golden Cap and Rhodesia
showing
hem
ore
minerals are predominantly hematite with lesser magnetite and trace
hem
pyrite and ilmenite
locally only hematite or predominantly magnetite with lesser hematite
euhedral to subhedral grains, large range of grain-sizes
multiple generations of hematite and magnetite precipitation (hematite
replacing magnetite and vice versa)
silica and carbonate alteration
Mag
Petrography (bFeOx)
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iron-oxide-albite-quartz breccia, varies in width (m-10’s m)
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flanking massive iron oxide in gradational contact
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ore minerals are predominantly hematite with lesser magnetite and trace
pyrite and ilmenite
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clast-supported breccia with anhedral grains of albite and quartz and veins
of iron-oxide
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multiple generations of hematite and magnetite precipitation (hematite
replacing magnetite and vice versa)
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chlorite, silica and carbonate alteration
Petrography (bFeOx)
feox
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iron-oxide-albite-quartz
breccia, varies in width (m-10’s m)
qtz
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flanking massive iron oxide in gradational contact
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ore minerals are predominantly hematite with lesser magnetite and trace
pyrite and ilmenite
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clast-supported breccia with anhedral grains of albite and quartz and veins
of iron-oxide
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multiple generations of hematite and magnetite precipitation (hematite
replacing magnetite and vice versa)
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chlorite, silica and carbonate alteration
alb
Petrography (bFeOx)
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iron-oxide-albite-quartz breccia, varies in width (m-10’s m)
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flanking massive iron oxide in gradational contact
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ore minerals are predominantly hematite with lesser magnetite and trace
pyrite and ilmenite
•
clast-supported breccia with anhedral grains of albite and quartz and veins
of iron-oxide
•
multiple generations of hematite and magnetite precipitation (hematite
replacing magnetite and vice versa)
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chlorite, silica and carbonate alteration
Petrography (bFeOx)
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Cu-mineralization at about 200m depth below surface
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associated with chl-alteration
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discovered at the bottom of the deepest drill-hole in 2008
mag
cpy
py
hem
Petrogenesis
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stable isotopes:
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quartz and albite from the iron-oxide breccia, coexisting with magnetite
yield temperatures in the range of 340 to 400 °C
Petrogenesis
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fluid inclusions:
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fluid inclusions record original fluid composition and PT-conditions
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quartz from iron-oxide breccia hosts 2 fluid populations
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carbonic present (CP) and carbonic absent (CA)
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both fluid populations are very saline
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eutectic melting temperatures
below NaCl-H20 system
eutectic (-21 °C)
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other salts than NaCl
present Æ KCl or CaCl
Petrogenesis
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combination of stable isotope data with isochores from fluid
inclusions constrains mineralization to depth of least 5km
(1750 – 4500 bars)
Petrogenesis
IRFZ
Aldridge Fm.
Aldridge Fm.
low P
high P
fluids
Petrogenesis
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fluid and heat-source:
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Cretaceous Mt. Skelly Pluton ~10 km
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Carboniferous? Carbonatites, occur locally
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Proterozoic Moyie Sills, occur locally
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basinal derived fluids
Geochronology
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Paleomag (PM), due to lack of dateable primary minerals
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PM has been successfully used in dating MVT and SEDEX
deposits around the world i.e.:
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HYC-Sedex, Australia by D.T.A. Symons (2007)
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Red-Dog MVT, Alaska by M.T. Lewchuk, D.L. Leach, Kelley,
K.D. and D.T.A Symons (2004)
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Navan-MVT, Ireland by D.T.A. Symons, M.T. Smethurst and J.H.
Ashton (1997)
Geochronology
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~100 collected samples were analyzed at the GSC-PGC
(Sidney, BC)
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PM has limitations, but could point towards one of the known
heat sources in the area
Geochronology
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Results:
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Iron Range FeOx are
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excellent carriers for remanent magnetization (single domain
hematite and magnetite)
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very stable
lightning and other sec. remanent magnetizations have been
successfully removed Æ PRM (primary remanent magnetization)
Geochronology
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Results:
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…however data was somewhat scattered
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because of multiple FeOx-precipitation events which locally
created a magnetic field
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subsequent ferromagnetic hematite and magnetite grains will
inherit ambient field when created PLUS the locally created
magnetic field of previously formed FeOx
Geochronology
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Results:
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nonetheless, general trend is observable towards a Cretaceous
direction (not all samples demagnetized completely)
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one site recorded a true reversal of the magnetic field (samples
with one 8cm drill-core)
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~avg. duration of a reversal is 10,000 years
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time span between 2 iron-oxide precipitation events
~ 10, 000 yrs
Geochronology
IR sites
Geochronology
IR sites
“Bathozonal Tilt Corrections to Paleomagnetic Data
From Mid-Cretaceous Plutonic Rocks: Examples
From the Omineca Belt, British Columbia” by E. Irving
and D.A Archibald (1990)
IOCG Potential
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“Although there is broad agreement on what generally
constitutes this family of deposits, there is little consensus on
the characteristics of the geological systems and the processes
that form them” (M.D. Barton and D.A. Johnson, 2004)
IOCG Potential
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Iron Range shares many characteristics of iron-oxide-(Cu-Au) (IOCG)
deposits worldwide, which according to Hitzman (2000); Williams et al,
(2005); and Barton and Johnson (2004) are:
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hydrothermal veins, breccia and replacement ore styles in a specific structural
site
CO2-bearing fluid inclusions
associated magmatism with no clear spatial association at the structural level
of mineralization
abundant magnetite and hematite with a low Ti-content
extensive sodic and/or potassic alteration
(sub-economic) Cu and/or Au mineralization
Acknowledgments
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SFU
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GSC (TGI3 Cordillera)
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Eagle Plains Resources
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Derek Thorkelson
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Reid Staples
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Karin Fecova
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Tim Termuende
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Lara Loughrey
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Mike McCuaig
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Brad Robinsen
Kootenay Gold, Ruby Red Resources
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Craig, Sean and Mike Kennedy